Instant oatmeal has three main disadvantages...one, noted by several posters already, is that it typically has excessive sugar added. Another, which was partly mentioned, is the glycemic index (GI)...it is higher compared to other forms of oatmeal, BECAUSE it is chopped up into tiny little pieces that will heat and hydrate very quickly. This factor improves as the pieces get larger...regular rolled oats, thick (or "hearty")-rolled oats, steel-cut oats, etc. Your body can digest and process those tiny pieces much more quickly than the large ones (hence the high GI and spike in blood sugar, helped along by the added sugar)...it is better, if possible to go with the largest form you have time for (yes, they progressively take longer to cook).
However, the regular rolled oats, cooked in a microwave with water (or milk, or juice), really don't take any longer than heating water for the instant oatmeal (just a few minutes). For travel, you could make some snack-size Ziplocs filled with 1 serving (~40g, or whatever you like) rolled oats (regular, not quick-cooking), with dried fruit and/or a SMALL amount of sugar or brown sugar JUST enough to make it palatable for you (you may not need additional sugar if you use dried fruit). You can use dried cranberries, chopped dried apricots, raisins...You could also add dry spices like cinnamon. If you have access to milk or orange juice where you are traveling, you could make the oatmeal with that (or half each) instead of water, again negating the need for added sugar. You can even take the thick-cut oatmeal and do this, if you can wait 8-10 minutes for the microwave to do its thing on a lower power setting (30-50%), taking care to use a container big enough to handle "bubbling up". If all you have access to is non-microwave hot water though (like something from a coffee machine), you'll have to stick with instant. You could try to make your own by chopping up rolled oats in a food processor and adding flavorings as above.
Finally, the commercial, processed instant oatmeals usually have some added chemicals to "preserve" or "enhance" or artificially flavor. Your own travel packages can avoid this.
Note: you can also take (in a separate bag) chopped or sliced toasted nuts to put on top after you cook the oatmeal, so even if you have to settle for the "slimier" instant (small-piece) style, you can still have something crunchy and more substantial to bite into (plus it adds lots of great nutrition).
